The carpal tunnel is an opening through the wrist into the hand that is formed by the carpal bones of the wrist on the bottom and the transverse carpal ligament on the top. The transverse carpal ligament is at the base of the wrist and crosses from one side of the wrist to the other. It is sometimes referred to as the carpal ligament or the flexor retinaculum.
The median nerve and flexor tendons of the hand run through the carpal tunnel. The median nerve rests on top of the flexor tendons, just below the carpal ligament. It gives sensation to the thumb, index finger, long finger, and half of the ring finger. It also sends a nerve branch to control the muscles of the thumb.
In general, carpal tunnel syndrome (CTS) develops when the tissues around the median nerve swell and press on the nerve. Early in the disorder, the process is reversible. Over time, however, the insulation on the nerves may wear away, and permanent nerve damage and severe loss of hand function may develop, along with pain, numbness, and tingling in the wrist, hand, and fingers. Only the little finger is unaffected by the median nerve.
Virtually all workers who use their hands and wrists repetitively are at risk for CTS, particularly if they work in cold temperatures and have factors or medical conditions that make them susceptible. For example, computer users/typists, workers in the meat and fish packing industries, airplane assemblers, and musicians are among those at very high risk for CTS. In addition, people who intensively cook, knit, sew, do needlepoint, play computer games, do carpentry, or extensively use power tools are likewise at increased risk for CTS.
Ideally, the early phases of carpal tunnel syndrome are treated before the damage progresses. A conservative approach to CTS, which may include corticosteroid injections and splinting, is typically the first step in treating this disorder. The conservative approach is most successful in patients with mild carpal tunnel syndrome. A concurrent regimen of physical therapy (e.g., a program of hand/wrist stretching and strengthening) may provide further benefits. In addition, alternative therapies such as ultrasound, nonsteroidal anti-inflammatory drugs (NSAIDs), ice/warmth, low-level laser therapy (LLLT), dietary modification, and acupuncture have been used in the treatment of CTS, with varying degrees of success.
For severe cases of CTS, surgery may be a more effective treatment option. Surgery is also more likely to be necessary for patients with underlying conditions such as diabetes. Even among patients with mild CTS, there is a high risk of relapse. Some researchers are reporting better results when specific exercises for carpal tunnel syndrome are added to the program of treatments.
Traditionally, in a CTS surgery, the carpal ligament is cut free (“released”) from the median nerve, thereby relieving the pressure on the median nerve. The most common approach has been an open surgical procedure (“open carpal tunnel release” or “open release”) performed in an outpatient facility, and is a straightforward and well-characterized procedure.
In recent years, more surgeons have adopted a “mini” open—also called short-incision—procedure. This surgery requires only a one-inch incision, but it still allows a direct view of the area (unlike endoscopy, which is viewed on a monitor). The mini-open approach may allow for quicker recovery while avoiding some of the complications of endoscopy, although few studies have investigated its benefits and risks. The recovery time in patients receiving the mini-open approach may be shorter than with the open approach, and results are generally the same.
Endoscopy for CTS is another less invasive procedure than standard open release. In an endoscopic release procedure, a surgeon makes one or two ½-inch incisions in the wrist and palm, and inserts one or two endoscopes (pencil-thin tubes). The surgeon then inserts a tiny camera and a knife through the lighted tubes. While observing the underside of the carpal ligament on a screen, the surgeon cuts the ligament to free the compressed median nerve.
Endoscopic release patients report less pain than those who had the open release procedure, and return to normal activities in about half the time. Nevertheless, at this time the best evidence available does not show any significant long-term advantages of endoscopy over open release in terms of muscle, grip strength, or dexterity. The endoscopic approach may even carry a slightly higher risk of pain afterward. This may be due to a more limited view of the hand with endoscopy. Concerns of irreversible nerve injury with endoscopic carpal tunnel release, when compared with open carpal tunnel release, exist because of this reduced visibility.
Regardless of the procedure, patients who have undergone conventional CTS surgery typically report some permanent loss of grip strength, a loss of lifting strength in the wrist/forearm and nagging loss of full range of motion of the hand and wrist after surgery. This is due to the severing of the carpal ligament. The purpose of the carpal ligament is to wrap around the hand and wrist and hold the many small bones of the hand and wrist securely together. The carpal ligament also maintains the flexor tendons in a path that enables the mechanical advantage necessary for strong grip strength and range of motion. These support capabilities are naturally diminished when the ligament is severed.
Accordingly, it is desirable to provide a system and technique for alleviating the symptoms of CTS while maintaining as much grip strength and/or range of motion of the hand and wrist.